Anti-neovascular therapy by use of tumor neovasculature-targeted long-circulating liposome.

For the purpose of cancer anti-neovascular therapy (ANET), we previously isolated 5-mer peptide Ala-Pro-Arg-Pro-Gly (APRPG) that specifically bound to the tumor angiogenic site and observed that APRPG-modified liposomes encapsulating adriamycin were effective for the suppression of tumor in tumor-bearing mice. Since polyethylene glycol (PEG) modification of liposomes endows them with a future of long circulation, we modified liposomes with PEG and APRPG-conjugated distearoylphosphatidylethanolamine (DSPE-PEG-APRPG) and examined the applicability of the liposomes on ANET. Liposomes containing DSPE-PEG-APRPG not only specifically bound to vascular endothelial growth factor-stimulated human umbilical vein endothelial cells in vitro, but also showed long-circulating characteristic and enhanced accumulation in tumor in vivo. Furthermore, adriamycin-encapsulated liposomes modified with APRPG-PEG caused more efficient tumor growth suppression than adriamycin-encapsulated liposomes modified with PEG alone in Colon 26 NL-17 carcinoma-bearing mice, despite not so much different accumulation of both liposomes in the tumor. These data suggest that tumor neovasculature-targeted long-circulating liposomes encapsulating anti-cancer drugs effectively eradicate cancerous cells through damaging of angiogenic endothelial cells. ANET promises no drug resistance and is expected to be effective against essentially any kind of solid tumors. The present results demonstrate the beneficial usage of APRPG-PEG for the active-targeting of drug carriers to angiogenic site in the novel modality of tumor treatment, namely ANET.

Synthesis of angiogenesis-targeted peptide and hydrophobized polyethylene glycol conjugate.

For the purpose of cancer antineovascular therapy, a novel angiogenesis-targeted peptide, Ala-Pro-Arg-Pro-Gly, (APRPG) was attached to hydrophobized polyethylene glycol (distearoylphosphatidylethanolamine [DSPE]-PEG). DSPE-PEG and the 5-mer peptide were condensed with DCC-HOBt method. Liposome modified with this DSPE-PEG-APRPG conjugate highly accumulated in tumor of tumor-bearing mice.

Cancer chemotherapy by liposomal 6-[12-(dimethylamino)ethyl]aminol-3-hydroxy-7H-indeno[2,1-clquinolin-7-one dihydrochloride (TAS-103), a novel anti-cancer agent.

A novel anti-tumor agent, 6-[[2-(dimethylamino)ethyl]amino]-3-hydroxy-7H-indeno[2,1-c]quinolin-7-one dihydrochloride (TAS-103), effectively inhibits both topoisomerase I and II activities. To enhance anti-tumor efficacy and to reduce the side effects of the agent, liposomalization of TAS-103 was performed. TAS-103 was effectively entrapped in liposomes by a remote-loading method, and was stable at 4 degrees C and in the presence of 50% serum. To evaluate the anti-tumor efficacy of liposomal TAS-103, the growth inhibition against Lewis lung carcinoma cells in vitro and the therapeutic efficacy against solid tumor-bearing mice in vivo were examined. Liposomal TAS-103 showed strong cytotoxic effect against Lewis lung carcinoma cells in a dose dependent manner and effectively suppressed solid tumor growth accompanying longer survival time of tumor-bearing mice in comparison with the mice treated with free TAS-103. These results suggest that liposomal TAS-103 is useful for cancer therapy.

Salacia reticulata and its polyphenolic constituents with lipase inhibitory and lipolytic activities have mild antiobesity effects in rats.

Salacia (S.) reticulata, a Hippocrateaceae plant distributed in Sri Lankan and Indian forests, has been used as a supplementary food in Japan to prevent obesity and diabetes. We examined the antiobesity effects of the hot water-soluble extract (SRHW) from the roots of S. reticulata using obese rat models and an in vitro study. Body weight (P = 0.07) and periuterine fat storage (P = 0.10) in female Zucker fatty rats (8-9 wk old) tended to be suppressed by oral administration of SRHW (125 mg/kg) for 27 d. Male rats fed a high fat diet were not affected by SRHW. Furthermore, SRHW inhibited porcine pancreatic lipase (PL), rat adipose tissue-derived lipoprotein lipase (LPL) and glycerophosphate dehydrogenase (GPDH) activities with 50% inhibitory concentrations (IC(50)) of 264 (95% confidence limits: 203-393) mg/L, 15 (12-18) mg/L and 54 (35-85) mg/L, respectively, but did not inhibit hormone-sensitive lipase activity in rat adipose tissue. Next, we examined the effects of polyphenols, di- and triterpenes and salacinol isolated from the roots of S. reticulata on lipid metabolizing enzymes and lipolysis. (-)-Epigallocatechin and (-)-epicatechin-(4beta-->8)-(-)-4'-O-methylepigallocatechin inhibited PL activity with IC(50) of 88 (not calculated) and 68 (26-122) mg/L, respectively. (-)-Epicatechin, 3beta, 22beta-dihydroxyolean-12-en-29-oic acid and the tannin fraction inhibited LPL activity with IC(50) of 81 (54-214), 89 (62-214) and 35 (24-62) mg/L. Only the tannin fraction inhibited GPDH activity with an IC(50) of 6.8 (3.4-10.9) mg/L. These constituents may be involved in the lipase and GPDH inhibitory activities of SRHW. On the other hand, SRHW at 100 mg/L tended to enhance lipolysis in rat adipocytes (P = 0.06). Significant lipolytic effects were exerted by mangiferin, (-)-4'-O-methylepigallocatechin and maytenfolic acid at 100 mg/L (P < 0.01). In conclusion, polyphenolic compounds may be involved in the antiobesity effects of SRHW in rats through inhibition of fat metabolizing enzymes (PL, LPL and GPDH) and enhanced lipolysis.

Potential usage of liposomal 4beta-aminoalkyl-4'-O-demethyl-4-desoxypodophyllotoxin (TOP-53) for cancer chemotherapy.

To enhance the therapeutic efficacy as well as to reduce the side effect, we attempted to liposomalize 4beta-aminoalkyl-4'-O-demethyl-4-desoxypodophyllotoxin (TOP-53), a novel and effective topoisomerase II inhibitor. More than 90% of TOP-53 was efficiently incorporated into the liposomes composed of dipalmitoylphosphatidylcholine and cholesterol by remote-loading method. Anti-tumor activity of liposomal TOP-53 against solid tumor was examined in vivo using colon26 NL-17 carcinoma model mice. Three doses of liposomal TOP-53 (12 mg/kg/dose) showed significant tumor growth suppression (97.5% reduction determined at day 25) and the increase in life span (33%) of tumor-bearing mice. Furthermore, one mouse out of 5 was completely cured after treatment. Since similar efficacy was observed in the free TOP-53 treated group, liposomalization does not contribute much to the enhancement of therapeutic efficacy. However, a slight but measurable damage at the injection site was observed when free TOP-53 was injected, and the damage was diminished by the liposomalization. Taken together, liposomalization reduces the side effect rather than enhancing the therapeutic efficacy when TOP-53 is used.